The influence of the extracellular potassium concentration on the glycoside effects upon contractile force and action potential duration of the guinea-pig papillary muscle

1966 ◽  
Vol 22 (10) ◽  
pp. 665-666 ◽  
Author(s):  
M. Reiter ◽  
F. J. Stickel ◽  
S. Weber
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Papillary Muscle ◽  
Action Potential Duration ◽  
Potassium Concentration ◽  
Contractile Force ◽  
Extracellular Potassium ◽  
Extracellular Potassium Concentration

scholarly journals Relationship between the effect of Goniopora toxin on action potential and contractile force in guinea pig papillary muscle

1979 ◽  
Vol 29 ◽  
pp. 156
Author(s):  
Motohatsu Fujiwara ◽  
Ikunobu Muramatsu ◽  
Shinobu Ikushima ◽  
Katsuro Ashida ◽  
Hiroyoshi Hidaka
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Papillary Muscle ◽  
Contractile Force ◽  
Goniopora Toxin

Sensory neurons in leech central nervous system: changes in potassium conductance an excitation threshold

1976 ◽  
Vol 39 (6) ◽  
pp. 1184-1192 ◽  
Author(s):  
W. R. Schlue
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Membrane Potential ◽  
Action Potential ◽  
Sensory Neurons ◽  
Potassium Concentration ◽  
Potassium Conductance ◽  
Extracellular Potassium ◽  
Extracellular Potassium Concentration ◽  
Accommodation Coefficients

1. The sensory neurons in the leech central nervous system differ in their accommodation to linearly rising currents. Advantage was taken of these differences to study the ionic mechanism of accommodation in single pairs of N (noxious), P (pressure), and T (touch) cells. 2. Nonlinearities in membrane-potential changes and current-voltage relationships with square-wave and ramp currents are more pronounced in P and T cells than in N cells. The accommodation coefficients increase in conditions that reflect this delayed rectification. When rectification is absent, the accommodation coefficients depart from unity only slightly or not at all. 3. Accommodation coefficients remain unchanged when half of the chloride in the bathing medium is replaced by sulfate. Accommodation coefficients become greater when the extracellular potassium concentration is reduced from 4 to 0 mM, and decrease when the concentration is raised to 8 mM. The membrane potential changes by only a few millivolts. 4. As extracellular potassium concentration is increased, the action potential is lengthened and the maximal rate of fall of the action potential is reduced. With concentrations greater than 4 mM these relationships are linear, but depart from linearity at lower concentrations. The amplitude of the undershoot decreases linearly as the extracellular potassium concentration increases from 4 to 16 mM, and increases non-linearly at concentrations below 4 mM. 5. The rapid accommodation of leech neurons is based primarily on an increased potassium conductance. The possibility is considered that concentration changes like those produced experimentally may occur naturally, affecting integrative processes in the central nervous system.

scholarly journals Myocardial Depressant Effects of Sevoflurane

1996 ◽  
Vol 84 (5) ◽  
pp. 1166-1176 ◽  
Author(s):  
Wyun Kon Park ◽  
Joseph J. Pancrazio ◽  
Chang Kook Suh ◽  
Carl III Lynch
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Guinea Pig ◽  
Action Potential ◽  
Papillary Muscle ◽  
Action Potential Duration ◽  
Action Potentials ◽  
Peak Force ◽  
Rapid Cooling ◽  
K Current ◽  
Slow Action Potentials

Background The effects of anesthetic concentrations of sevoflurane were studied in isolated myocardial tissue to delineate the mechanisms by which cardiac function is altered. Methods Isometric force of isolated guinea pig ventricular papillary muscle was studied at 37 degrees C in normal and 26 mM K+ Tyrode's solution at various stimulation rates. Normal and slow action potentials were evaluated using conventional microelectrodes. Effects of sevoflurane on sarcoplasmic reticulum function in situ were also evaluated by its effect on rapid cooling contractures, which are known to activate Ca2+ release from the sarcoplasmic reticulum, and on concentrations of rat papillary muscle. Finally, Ca2+ and K+ currents of isolated guinea pig ventricular myocytes were examined using the whole-cell patch clamp technique. Results Sevoflurane equivalent to 1.4% and 2.8% depressed guinea pig myocardial contractions to approximately 85 and approximately 65% of control, respectively, although the maximum rate of force development at 2 or 3 Hz and force in rat myocardium after rest showed less depression. In the partially depolarized, beta-adrenergically stimulated myocardium, sevoflurane selectively depressed late peak force without changing early peak force, whereas it virtually abolished rapid cooling contractures. Sevoflurane did not alter the peak amplitude or maximum depolarization rate of normal and slow action potentials, but action potential duration was significantly prolonged. In isolated guinea pig myocytes at room temperature, 0.7 mM sevoflurane (equivalent to 3.4%) depressed peak Ca2+ current by approximately 25% and increased the apparent rate of inactivation. The delayed outward K+ current was markedly depressed, but the inwardly rectifying K+ current was only slightly affected by 0.35 mM sevoflurane. Conclusions These results suggest that the direct myocardial depressant effects of sevoflurane are similar to those previously described for isoflurane. The rapid initial release of Ca2+ from the sarcoplasmic reticulum is not markedly decreased, although certain release pathway, specifically those induced by rapid cooling, appear to be depressed. Contractile depression may be partly related to the depression of Ca2+ influx through the cardiac membrane. The major electrophysiologic effect of sevoflurane seems to be a depression of the delayed outward K+ current, which appears to underlie the increased action potential duration.

scholarly journals Relationship between the effects of Goniopora toxin on action potential and on contractile force in guinea-pig papillary muscle.

1981 ◽  
Vol 31 (6) ◽  
pp. 1051-1060 ◽  
Author(s):  
Shinobu IKUSHIMA ◽  
Ikunobu MURAMATSU ◽  
Motohatsu FUJIWARA ◽  
Katsuro ASHIDA
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Papillary Muscle ◽  
Contractile Force ◽  
Goniopora Toxin
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